[PATCH] Display 0 in meminfo for Committed_AS when value underflows

[Eric B Munson <ebmunson@us.ibm.com>]

Andrew,

Please merge the following patch.

Splitting this patch from the chunk that addresses the cause of the underflow
because the solution still requires some discussion.

Dave Hansen reported that under certain cirumstances the Committed_AS value
can underflow which causes extremely large numbers to be displayed in
meminfo.  This patch adds an underflow check to meminfo_proc_show() for the
Committed_AS value.  Most fields in /proc/meminfo already have an underflow
check, this brings Committed_AS into line.

Reported-by: Dave Hansen <dave@linux.vnet.ibm.com>
From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Eric B Munson <ebmunson@us.ibm.com>
---
 fs/proc/meminfo.c |    4 +++-
 1 files changed, 3 insertions(+), 1 deletions(-)

diff --git a/fs/proc/meminfo.c b/fs/proc/meminfo.c
index 74ea974..facb9fb 100644
--- a/fs/proc/meminfo.c
+++ b/fs/proc/meminfo.c
@@ -22,7 +22,7 @@ void __attribute__((weak)) arch_report_meminfo(struct seq_file *m)
 static int meminfo_proc_show(struct seq_file *m, void *v)
 {
 	struct sysinfo i;
-	unsigned long committed;
+	long committed;
 	unsigned long allowed;
 	struct vmalloc_info vmi;
 	long cached;
@@ -36,6 +36,8 @@ static int meminfo_proc_show(struct seq_file *m, void *v)
 	si_meminfo(&i);
 	si_swapinfo(&i);
 	committed = atomic_long_read(&vm_committed_space);
+	if (committed < 0)
+		committed = 0;
 	allowed = ((totalram_pages - hugetlb_total_pages())
 		* sysctl_overcommit_ratio / 100) + total_swap_pages;
 
-- 
1.6.1.2

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